Planning for PSTN connectivity in Lync Server 2013

An enterprise-grade VoIP solution must provide for calls to and from the public switched telephone network (PSTN) without any decline in Quality of Service (QoS). Users who place and receive calls should not be aware of the underlying technology: from the user's perspective, a call between the Enterprise Voice infrastructure and the PSTN should seem like just another phone call.

Lync Server 2013 provides reliable, scalable PSTN connectivity by using the following options:

SIP trunks to an Internet telephony service provider (ITSP)

Direct SIP connections to a PSTN gateway

Direct SIP connections to a PBX

Depending on its size, geographic coverage, and existing voice infrastructure, an enterprise may use one, two, or even all three of these options at various locations.